feat: add bash shell utility functions

12 funciones Bash del dominio shell: utilidades de scripting (bash_log,
bash_colors, bash_check_deps, bash_confirm, bash_handle_error, bash_safe_run),
manipulacion de texto (convert_text_case), estructura de proyectos
(create_project_structure), y operaciones git (git_clean_branches,
git_log_visual, git_push_all_remotes, git_repo_status). Cada una con su
.sh y .md de frontmatter.

bash/functions/shell/bash_log.sh

@@ -0,0 +1,64 @@
+# bash_log
+# --------
+# Funciones de logging con colores para scripts.
+# Incluye: log, success, info, warning, error, debug, progress.
+#
+# USO (sourced):
+#   source bash_log.sh
+#   bash_log_init
+#   success "Operacion completada"
+#   info "Procesando..."
+#   error "Algo fallo"
+
+SCRIPT_DIR_BASH_LOG="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR_BASH_LOG/bash_colors.sh"
+bash_colors
+
+bash_log_init() {
+    export ERROR_LOG_FILE="${ERROR_LOG_FILE:-/tmp/script-errors-$(date +%Y%m%d).log}"
+    export DEBUG_MODE="${DEBUG_MODE:-0}"
+}
+
+log() {
+    local level="$1"
+    shift
+    local message="$@"
+    local timestamp
+    timestamp=$(date '+%Y-%m-%d %H:%M:%S')
+    echo "[$timestamp] [$level] $message" >> "${ERROR_LOG_FILE:-/tmp/script-errors.log}"
+
+    if [ "${DEBUG_MODE:-0}" = "1" ]; then
+        echo -e "${GRAY}[$timestamp] [$level] $message${NC}" >&2
+    fi
+}
+
+success() {
+    echo -e "${GREEN}${CHECKMARK} $*${NC}"
+    log "SUCCESS" "$*"
+}
+
+info() {
+    echo -e "${BLUE}${INFO} $*${NC}"
+    log "INFO" "$*"
+}
+
+warning() {
+    echo -e "${YELLOW}${WARNING} $*${NC}"
+    log "WARNING" "$*"
+}
+
+error() {
+    echo -e "${RED}${CROSS} Error: $*${NC}" >&2
+    log "ERROR" "$*"
+}
+
+debug() {
+    if [ "${DEBUG_MODE:-0}" = "1" ]; then
+        echo -e "${GRAY}[DEBUG] $*${NC}" >&2
+    fi
+    log "DEBUG" "$*"
+}
+
+progress() {
+    echo -e "${CYAN}${ARROW} $*${NC}"
+}